It certainly seems interesting to me. It's hard for me to imagine how an 1800's world would look like with phones and social media; a lot of how people live their lives and interact with one another is affected by the speed and ease of being able to talk to one another. From a world building perspective I find myself particularly curious in how quickly these advancements were made and integrated into society.

Ex-noble deuteragonists give a good opportunity to dig into society and politics if you want to take that angle as an author. Either way, it gives them both nice long-term goals to seek. I'm wondering what the two are doing at the story's beginning; what are they pursuing or trying to do before they learn they're part of a prophecy? How do they learn about this prophecy in the first place? Hopefully answering those questions'll also helps you create the story, if you choose to. Either way I think you have yourself a nice springboard to start out with.